1. Technical Field
The present invention relates to a medium feeding device that feeds a medium, a scanner having the same and a recording apparatus having the same.
2. Related Art
Ink jet printers are an example of recording apparatuses. Recently, so-called multifunction machines which incorporate scan function in addition to print function have gained popularity as ink jet printers. Multifunction machines are capable of performing both reading of a document and recording on a sheet of paper, which provide convenience to a user and save the installation space.
Scanners sometimes include an automatic feeder (also known as auto document feeder (ADF)) and are configured to perform automatic feeding and reading of a plurality of documents. For example, JP-A-2010-28546 discloses a configuration of document automatic feeder in which a document is fed out from a document tray, turned to the opposite direction around a roller, transported to a reading position, and then output to an output tray.
In such automatic document feeders, and also in sheet feeding units of ink jet printers, it is important to separate a medium to be fed and the subsequent media with certainty so as to prevent the subsequent media from being fed along with the medium to be fed.
In order to prevent such double-feed, a friction pad or projection (such as claw and hook) is typically used as a separation unit, for example as described in JP-A-5-77959 and JP-A-11-49395. Moreover, JP-A-2010-28546 and JP-A-5-77959 discloses the use of two separation units, an upstream separation unit and a downstream separation unit, with the aim of further improving separation of the media.
Although JP-A-5-77959 and JP-A-11-49395 disclose a sheet feeder that is provided with two separation units so as to further improve separation of the sheets, the sheet feeder has a disadvantage in that the sheets may be double-fed when the leading edge of the sheet is curled. In particular, since the downstream separation unit of the sheet feeder disclosed in JP-A-5-77959 and JP-A-11-49395 is formed by a projection, it is highly possible that separation of the sheets is not performed when the leading edge of the sheet is curled in a direction in which the leading edge does not interfere with the projection.